AGING AND TIME TO INSTABILITY IN POSTURE

Two experiments are reported that were set up to examine the spatial-t emporal boundaries of postural instability in upright stance as a func tion of age (60-96 years) and postural conditions. Subjects stood on a force platform under different experimental conditions (vision/no vis ion and arms up/down) so that the effect of age on key dynamic propert ies of postural stability could be determined. The findings showed tha t the ratio of the area of the motion of the center of pressure to the area within the stability boundary increased with age. Also, the virt ual time-to-contact with the postural stability boundary decreased wit h age. Collectively, the findings show that the margins to the spatial -temporal boundaries of postural stability decrease with advancing age in the elderly. These reduced margins of dynamic stability may be a f actor contributing to the progressive instability of posture with agin g in the elderly.